Process for the activation of a catalyst comprising a cobalt compound and a support

ABSTRACT

A process for the preparation of a catalyst which comprises activating a catalyst precursor comprising a cobalt compound and a support with a gas comprising at least 5 mol % of a hydrocarbon.

RELATED APPLICATIONS

This application is a continuation of U.S. application Ser. No.10/481,986, filed Dec. 23, 2003, U.S. Pat. No. 7,183,329, which is thenational stage of International Application No. PCT/GB02/02883, filedJun. 21, 2002, which claims the benefit of United Kingdom ApplicationNo. 0115850.0, filed Jun. 28, 2001.

TECHNICAL FIELD

The present invention relates to a catalyst and to a process for thepreparation of a catalyst, in particular a catalyst for use in thepartial oxidation of a hydrocarbon such as methane to synthesis gas orfor use in a Fischer-Tropsch synthesis reaction or other reactions.

BACKGROUND

Catalysts are well known to be useful in certain reactions. Inparticular they can be used to promote particular reactions which wouldnot normally take place in the absence of the catalyst.

An example of a reaction where a catalyst is useful is the production ofsyngas, which is a mixture of carbon monoxide and hydrogen in varyingproportions. It is known to produce syngas by a steam reforming reactionwherein steam and methane are passed over a catalyst. Such a reaction isendothermic.

Recently syngas has also been produced by the partial oxidation ofmethane (POM). In this process methane is partially oxidised with oxygenin the following reaction:CH₄+1/2O₂→CO+2H₂

The POM reaction has the great advantage of being exothermic, and hencedoes not require a great energy input. The process is described infurther detail, for example, in Choudhary et al, Fuel, vol. 77, No. 15,pp 1803-1807, 1998, Slagtern et al, Catalysis Today, 46, 107-115, 1998and WO 01/36,323. In a modification of this process, other hydrocarbonsmay be used as well as or instead of the methane. As used in thisspecification, the term “POM” is intended to cover not only the partialoxidation of methane but also the partial oxidation of any hydrocarbon.

The POM reaction generally uses a nickel or cobalt containing catalystor a noble metal catalyst. For example Choudhary et al discloses the useof various such catalysts. For example, a cobalt containing catalyst canbe prepared by mixing cobalt nitrate with a support such as silica geland deionised water to form a thick paste, mixing the paste and dryingand decomposing the paste in air at 600° C. for 4 hours before calciningthe catalyst at 900° C. for 4 hours. This reference also indicates thatthe catalysts may be reduced using hydrogen before they are used, butthat the performance of reduced and unreduced catalysts is comparable.It has also found that the best catalysts are nickel-containingcatalysts such as NiO—Tho₂, Ni—ZrO₂ and Ni—UO₂.

Another example of a process where a catalyst is useful is in a FisherTropsch synthesis reaction in which a mixture of hydrocarbons isproduced from carbon monoxide and H₂.

DETAILED DESCRIPTION OF THE INVENTION

We have now found a further catalyst which can be used in a variety ofreactions such as a POM or Fischer Tropsch reaction. We havesurprisingly found that this catalyst may have one or more advantagesover the known catalysts.

The present invention provides a process for the preparation of acatalyst which comprises activating a catalyst precursor comprising acobalt compound and a support with a gas comprising a hydrocarbon,especially at least 5 mol % of a hydrocarbon.

The present invention further provides the use of a catalyst obtainableby a process as defined above or a catalyst as defined above in thepartial oxidation of a hydrocarbon or in a Fischer Tropsch reaction.

The present invention yet further provides a process for the preparationof a mixture of hydrocarbons by a Fischer-Tropsch reaction, whichcomprises passing a mixture of carbon monoxide and H₂ over a catalystobtainable by a process as defined above or a catalyst as defined above.

The present invention additionally provides a process for the partialoxidation of a hydrocarbon which comprises passing such hydrocarbon andoxygen over a catalyst obtainable by a process as defined above or acatalyst as defined above.

As used herein, the term “catalyst” covers both the catalyst in activeform and the catalyst in precursor form since it may undergo change inthe reaction environment. The term “catalyst precursor” is to beconstrued widely, covering not only a freshly prepared catalystprecursor or a catalyst precursor which is unreduced or which has notbeen used in a reaction which it catalyses, but also any precursor whichcan be used as a catalyst after activation, such as a catalyst which hasalready been used in a reaction which it catalyses. Similarly the term“activation” is to be understood as not only including activating asunused or unreduced catalyst precursor but also activating a used orreduced catalyst. Therefore the term includes within its scope anyactivation, including regeneration of a used catalyst.

The process of the present invention uses an activation step with ahydrocarbon rather than with hydrogen as disclosed in, for example,Choudhary et al. It has surprisingly been discovered that such acatalyst may have advantageous characteristics such as a better activityand less susceptibility to deactivation over time.

The catalyst is prepared by activating a catalyst precursor with ahydrocarbon. The catalyst precursor contains a cobalt compound and asupport. Such catalyst precursors are known and disclosed in the priorart, for example in Choudhary et al.

The support may be any support which is capable of bearing the catalystin the desired reaction. Such supports are well known in the art. Thesupport may be an inert support, or it may be an active support.Examples of suitable supports are alumina, modified alumina, spineloxides, silica, modified silica, magnesia, titania, zirconia, a zeolite,β-aluminate and forms of carbon. The alumina or modified alumina may be,for example, α-alumina, β-alumina or γ-alumina. β-alumina and spineloxides such as barium hexaaluminate have been found to be particularlyuseful in view of their stability. The carbon may be in the form, forexample, of active carbon or carbon nanotubes. A zeolite may be chosendepending on the desired final product. Thus, for example, it maycomprise pores or channels.

Preferably the support is porous. The particle size is desirably 0.2 μmto 0.4 mm, depending on the application. The surface area is desirablygreater than 5 m²/g. One or a mixture of two or more supports may beused.

The catalyst precursor also comprises a cobalt compound. Any cobaltcompound may be used, but preferably it is in the form of a salt,especially an aqueous soluble salt, or oxide. Examples of suitablecobalt salts are cobalt nitrate, acetate, benzoate, oxalate andacetylacetonate. It is preferred to avoid the use of a cobalt halidesince the halide may interfere with the support. An example of asuitable cobalt oxide is CO₃O₄. One or a mixture of two or more cobaltsalts and/or oxides may be used.

The catalyst precursor is supported on the support. Depending on thenature of the reaction to be catalysed, the catalyst precursor may bedistributed in any desired way on or in the support. Thus it may, forexample, be distributed substantially throughout the support or only onthe external surface of the support.

The catalyst precursor may be supported in any known manner. Thus itmay, for example, be added to the support in solution in a solvent suchas water or an organic solvent such as an alcohol, for examplecontaining from 1 to 4 carbon atoms such as an methanol or ethanol andthe solvent subsequently removed. The solvent may be removed, forexample, by drying at room temperature (20° C.) or above, for examplefrom 50° C. to 250° C. for from 1 to 24 hours. A combination of dryingsteps may be used. Thus, for example, the supported catalyst precursormay be dried at room temperature for from 2 to 10 hours, andsubsequently dried at an elevated temperature, for example from 100° C.to 200° C., especially about 120° C., for from 2 to 8 hours.

The solution comprising the catalyst precursor may comprise furthercomponents if desired. Thus, for example, it may also comprise apromoter or modifier. Suitable promoters are alkaline earth salts suchas magnesium, calcium, barium and/or strontium nitrate.

Suitable promoters also include the oxides of alkali metal, alkalineearth metal or transition metals which are derivable from their solublecompounds, such as their salts, for example LiNO₃, KNO₃, RbNO₃,Ba(NO₃)₂, Mg(NO₃)₂, Ca(NO₃)₂, Sr(NO₃)₂, Zr(NO₃)₂.xH₂O, Ce(NO₃)₃.xH₂O andUO(NO₃)₂. The promoters can be loaded onto the support in any manner,for example by impregnation, especially sequential impregnation orco-impregnation with the cobalt compound.

Suitable modifiers are rare earth modifiers such as transition metal orrare earth salts or oxides, for example lanthanum and/or cerium nitrateor acetate, or oxides of the d-block transition metals such as Mn, W, Nband Vn. The modifiers are generally derived from their aqueous solublecompounds such as salts, and may be impregnated into the catalystsupport, followed by calcination, for example from 300° C. to 1000° C.for 1 to 24 hours in air. The promoters and modifiers may be used singlyor in a combination of two or more. Preferably the supported catalystprecursor does not contain catalyst poisons such as phosphorus oxides,nitrogen oxides or sulphur oxides or compounds, and does not containcomponents having additional functionality such as absorbers,particularly absorbers for nitrogen oxides and/or sulphur oxides. Thesupported catalyst precursor, however, desirably comprises a promoterand/or a modifier.

The supported catalyst precursor may, if desired, be calcined.Calcination is not a required step in the process of the presentinvention. Calcination can take place in air, another gas comprisingoxygen or in an inert atmosphere. A suitable calcination temperature is,for example, from 350° C. to 800° C., especially from 400° C. to 600°C., for from 1 to 10 hours. It is postulated, although we are not boundby this theory, that the calcination step changes the cobalt salt intoan oxide form or mixture of oxide forms. The calcination step may alsoconvert the promoter and/or modifier to oxide forms if they are present.

The supported catalyst precursor desirably comprises from 0.05 to 30 wt% cobalt, especially 0.5 to 15 wt %. For example, the supported catalystprecursor generally comprises from 0.5 to 50 wt % cobalt compound, 0 to10 wt % promoter and 0 to 20 wt % modifier, especially 0.01 to 5 wt %modifier, based on the total weight of the supported catalyst precursor.For a POM reaction the supported catalyst precursor preferably comprisesfrom 0.5 to 10 wt % cobalt compound, 0 to 5 wt % promoter and 0 to 3 wt% modifier. For a Fischer-Tropsch reaction the supported catalystprecursor preferably comprises from 5 to 40 wt % cobalt compound, 0 to 3wt % promoter and 0 to 3 wt % modifier. The above percentages for thecobalt compounds are based either on the compound or the cobalt metal inthe compound.

The supported catalyst precursor is then activated with a gas comprisinga hydrocarbon. The hydrocarbon may be any hydrocarbon. It may besaturated or unsaturated, for example containing from 1, 2 or 3 or moredouble and/or triple bonds. It may be linear, cyclic or branched. Thehydrocarbon may also be aliphatic or aryl or contain both aliphatic andaryl groups. Desirably the hydrocarbon is a saturated or unsaturatedhydrocarbon containing up to five carbon atoms, especially up to fourcarbon atoms. Especially preferred hydrocarbons are methane, ethane,acetylene, propane, propene and butane. One or a mixture of two or morehydrocarbons may be used.

The gas comprises at least 5 mol % of the hydrocarbon, preferably atleast 10 mol %, more preferably at least 20 mol % and even morepreferably at least 40 mol %. The hydrocarbon is in gaseous form.

The gas comprising the hydrocarbon may consist only of the hydrocarbonor may, for example in an amount up to 10 mol %, up to 20 mol % or up to40 mol %. It may, if desired, comprise an inert gas such as nitrogenand/or argon. It may also comprise a reactive component, such as anothercomponent which also activates the catalyst precursor. Thus, forexample, the gas may also comprise hydrogen. Especially usefulcombinations are a combination of methane and/or ethane with hydrogen.If hydrogen is used any ratio of hydrocarbon to hydrogen may be used,but it is preferably 0.04 or 0.05 to 100:1 on a molar basis, morepreferably 0.1 or 0.5 to 10:1.

The activation is carried out by placing the supported catalystprecursor in an atmosphere of the activating gas. Desirably theactivating gas is passed over the supported catalyst precursor. Anelevated temperature is generally used. Desirably the activationtemperature is at least 300° C., for example from 400° C. to 1000° C.,especially from 400° C. to 800° C. The duration of activation isgenerally at least 30 minutes, preferably at least one hour, forexample, from 1 to 20 hours, especially from 2 to 5 hours. Theactivation temperature may vary depending on the nature of the catalystprecursor and/or the hydrocarbon. Atmospheric pressure is normally usedfor the activation step, although a reduced or elevated pressure mayalso, if desired, be used.

The catalyst precursor may be activated in the reaction vessel in whichit is intended to carry out the desired reaction using the activatedcatalyst, or it may be activated in a different vessel. The activatedcatalyst undergoes substantial oxidation when exposed to air. In orderto stabilize the catalyst it may be treated in an atmosphere containinga small amount of oxygen, for example about 1% oxygen in an inert gassuch as nitrogen or argon. Alternatively the catalyst can simply be leftin the activation reactor while bleeding in a small amount of oxygen.Thus, for example, the activated catalyst may be pacified by treatmentin a reduced oxygen atmosphere, for example comprising less than 20 mol% oxygen, less than 10 mol % oxygen, less than 5 mol % oxygen or lessthan 2 mol % oxygen, for at least 30 minutes, especially for at leastone hour. The resulting passified catalyst may now be handled or storedin air for brief periods without further substantial oxidation.

The supported catalyst precursor may also be formed by a sol gel method.Such a method is described, for example, in Gonzalez et al, CatalysisToday, 35 (1997), 293-317 and J. Livage, Catalysis Today, 41 (1998),3-19. For example, in an initial “pregelation” step, an alkoxide oralcohol and a metal precursor are hydrolysed and condensed to form agel, for example, in the presence of water. A cobalt compound is thenadded in a subsequent “post gelation” step and the gel is dried andcalcined.

For example aluminium-tri-sec-butylate (ASB) in 2-butanol is treatedwith 1,3-butandiol. A hydrolysis reaction occurs.Co(H₂O)₆(NO₃)₂(hydrated cobalt nitrate) is then added and the resultinggel stirred for 1 hour at 85° C. The solvent is removed under a flow ofair or N₂ at 40° C. to 100° C. for 2 to 3 hours. The solid product iscalcined at from 400° C. to 1,000° C. for 2 to 5 hours to produce thesupported catalyst precursor.

It is postulated, although we are not bound this theory, that theactivation of the catalyst precursor forms a mixture of metallic cobaltand cobalt carbides such as Co₂C and/or Co₃C on the support. XRDanalysis shows that, when H₂ is used to activate the same catalystprecursor, the Co metal peak intensity is much more intense than when ahydrocarbon is used, suggesting that the hydrocarbon gives rise tosmaller particles of cobalt metal than when hydrogen is used. Thisadvantageously increases the surface area of the cobalt metal, which inturn increases the catalyst efficiency. Thus the activated catalyst maycomprise carbon, in any form including elemental carbon and carbidessuch as cobalt carbides, in an amount of, for example, up to 20 wt %,especially 0.02 to 10 wt %.

The catalyst produced by the process of the present invention may beused in any process where a cobalt catalyst may be used, especially whena fixed or slurry bed reactor is used. Thus, for example, it may be usedin a POM reaction, Fischer-Tropsch reaction, a hydroisomerisationreaction or a hydrogenation reaction.

In a POM reaction a mixture of a hydrocarbon and oxygen is passed overthe catalyst to produce syngas. The hydrocarbon preferably contains from1 to 16 carbon atoms and more preferably from 1 to 5 carbon atoms. Mostpreferably it is methane or natural gas. The hydrocarbon may besaturated or unsaturated, for example containing from 1, 2, 3 or moredouble and/or triple bonds. It may be linear, cyclic or branched. Thehydrocarbon may also be aliphatic and aryl or contain both aliphatic andaryl groups. One or a mixture of hydrocarbons may be used.

In the POM reaction the oxidant is normally O₂. It may be pure O₂.However, it may be supplemented with H₂O (steam) or CO₂, for example byaddition to the feedstock. Thus O₂ and H₂O; O₂ and CO₂; or O₂, H₂O andCO₂ may be used. This results in oxy-steam or oxy-dry reforming ofmethane, respectively. By this means the exothermicity and product ratiomay be controlled as desired. The O₂, and optionally H₂O and CO₂ may beused pure or diluted with an inert gas such as air, N₂, Ar or He.

Desirably the reaction takes place at a temperature of at least 500° C.,for example from 700° C. to 1000° C. Desirably the pressure isatmospheric pressure (101 kPa) or above, for example from 1 to 60atmospheres (101 kPa to 6080 kPa), especially from 1 to 30 atmospheres(101 kPa to 3060 kPa). The space velocity of the reactants may be, forexample, from 1000 h⁻¹ to 1,000,000 h⁻¹, preferably 10,000 h⁻¹ to600,000 h⁻¹. The mole ratio of the hydrocarbon being oxidized and theoxygen is desirably chosen such that a mixture of carbon monoxide andhydrogen is obtained in a stoichiometric ratio. Thus, for example, theatomic ratio of carbon such as methane to oxygen in the feedstock isdesirably 0.9 to 5:1 or even higher, especially 1.0 or 1.8 to 3.5:1,more preferably 1 to 3:1, especially 1 to 2:1, especially about 1:1,although lower or higher ratios may also, if desired, be used.

It has been found that the catalyst produced by the process of thepresent invention usually has a number of advantages over cobaltcatalysts which have been activated using hydrogen. Thus, for example,the catalysts are stable over time and do not suffer a decrease inactivity. Furthermore the catalysts may have greater activity, forexample an activity approaching that of ruthenium catalysts, but withthe considerable advantage of being cheaper than ruthenium catalysts.Additionally it has been found that the catalysts produced by theprocess of the present invention do not promote carbon deposition, whichis extremely undesirable in industrial processes. Cobalt catalystsactivated with hydrogen typically suffer from carbon deposition afterabout 200 hours of use. The catalysts produced by the process of thepresent invention generally do not suffer from carbon deposition evenafter about 1000 hours of use.

The catalyst produced by the process of the present invention may alsobe used, for example, in a Fischer Tropsch synthesis reaction. Such areaction produces a mixture of hydrocarbons and/or oxygenatedhydrocarbons, for example gaseous, liquid and/or solid hydrocarbonsand/or oxygenated hydrocarbons such as alcohols, from a mixture ofhydrogen and carbon monoxide. Thus, for example, the reaction can becarried out immediately using syngas prepared by the POM method indirectly linked reactors as disclosed in, for example, WO 01/36,323.

In the Fischer-Tropsch reaction, hydrogen and carbon monoxide arereacted over the activated cobalt catalyst at a temperature of, forexample from 150 to 300° C. at atmospheric pressure (101 kPa) or above,for example from 1 atmosphere (101 kPa) to 20 atmospheres (2030 kPa).Similar advantages may be seen for the catalysts produced by the processof the present invention over those produced using pure hydrogen as anactivating gas as for the POM reaction discussed above. Thus, forexample, the catalyst may be more stable and/or more active. Similarly,it does not promote carbon deposition, and it may also be more selectiveto the desired mixture of hydrocarbons, especially hydrocarbonscontaining at least 5 carbon atoms. It may also produce a mixture ofhydrocarbons having a great degree of unsaturation.

The present invention is now further illustrated in the followingExamples.

EXAMPLE 1

1.0 g of Al₂O₃ support (particle size>250 μm, dried at 120° C. for 2 h)was impregnated with 1.0 ml of 0.2M Ba(NO₃)₂ solution. The mixture wasdried at 120° C. for 4 hours, followed by calcination at 600° C. for 4hours to obtain a BaO modified support. This modified support (1.05 g)was then impregnated with 1 ml of 2.4M Co(NO₃)₂ solution for 2 hours.The resulting solid was calcined to 600° C. to give the oxide precursorof the cobalt catalyst. This was then treated with 30 ml/min of 50%CH₄/H₂ at 800° C. for 2 h, and then cooled to room temperature in flowof 50% CH₄/H₂. The activated catalyst was treated with 1.0% O₂/N₂ atroom temperature for 6 hours, 0.1 g of the activated catalyst was placedin a quartz tube, heated to chosen reaction temperatures in N₂, then amixture of CH₄ and air was introduced into the reactor at 100 kPa (1bar). The reaction conditions and products are listed in Table 1.

TABLE 1 CH₄ conversion and product distribution from methane partialoxidation (POM) over 12.5 wt % Co/Al₂O₃—BaO catalysts activated with 50%CH₄/H₂ to 800° C. for 2 h Reaction CH₄ CO CO₂ temperature conversionselectivity selectivity H₂/CO (° C.) (%) (%) (%) ratio 600 57.60 56.5243.48 2.70 650 67.97 71.08 28.91 2.34 700 75.67 79.95 20.04 2.17 75083.53 87.63 12.36 2.01 800 91.07 91.93 8.06 1.99 Reaction conditions: P:100 kPa (1 bar), GHSV: 36,000 h⁻¹. Air was used as the oxidant.

EXAMPLE 2

1.0 g of Al₂O₃ support (particle size>250 μm) was impregnated with 1.0ml of 0.2M Ba(NO₃)₂ solution. The solid was dried at 120° C. for 4hours, and then calcined at 600° C. for 4 hours. The resulting BaOmodified support (Al₂O₃—BaO) (1.05 g) was impregnated with 1 ml of 2.4MCo(NO₃)₂ solution for 2 hours. The mixture was then calcined at 600° C.to give the oxide precursor of the catalyst. This was treated with 20%C₂H₆/H₂ flowing at 30 ml/min at 630° C. and held at 630° C. for 2 h. Thegas flow was stopped, and the reactor was cooled to room temperaturewithout exposure to air. The catalyst was then treated with 1.0% O₂/N₂for 3 h. 0.1 g of the ready-for-use cobalt catalyst was loaded to thequartz tube and heated to the chosen reaction temperature in N₂. Areactant mixture of CH₄ and air (CH₄/O₂ ratio, 2.01) was passed into thereactor at 100 kPa (1 bar). The reaction conditions and results arelisted in Table 2.

TABLE 2 CH₄ conversion and product distribution from POM over 12.5 wt %Co/Al₂O₃—BaO catalysts activated with 20% C₂H₆/H₂ to 630° C. for 2 hReaction CH₄ CO CO₂ temperature conversion selectivity selectivity H₂/CO(° C.) (%) (%) (%) ratio 600 60.74 63.92 36.08 2.60 650 71.81 71.0828.91 2.34 700 77.18 81.86 18.14 2.13 750 84.78 88.63 11.37 2.00 80092.05 93.93 6.07 1.99 Reaction conditions: P: 100 kPa (1 bar), GHSV:36,200 h⁻¹. Air was used as the oxidant.

EXAMPLE 3

1.0 g of Al₂O₃ support (particle size>250 μm) was impregnated with of1.0 ml 0.15M La(NO₃)₃ solution. The mixture was dried at 120° C. for 4 hand then calcined at 700° C. for 2 h. The resulting La₂O₃ modifiedsupport (Al₂O₃—La₂O₃) (1.05 g) was impregnated with 1 ml of 1.0 MCo(NO₃)₂ solution for 5 hours, and calcined to 700° C. It was thentreated with flowing CH₄ at 700° C. and held at 700° C. for 1 h, andthen cooled to room temperature without exposure to air. Then it wastreated with 1.0% O₂/N₂ at room temperature for 10 h. The ready-for-usecatalyst (0.1 g) was loaded in a quartz tube and heated to the chosenreaction temperatures in 10 ml/min of CH₄. A mixture of CH₄ and pureoxygen (CH₄/O₂ ratio, 2.01) was passed into the reactor at 100 kPa (1bar). The reaction conditions and product distribution are listed inTable 3.

TABLE 3 CH₄ conversion and product distribution from POM over 5.6 wt %Co/Al₂O₃—La₂O₃ catalysts activated with pure CH₄ to 700° C. for 2 hReaction CH₄ CO CO₂ temperature conversion selectivity selectivity H₂/CO(° C.) (%) (%) (%) ratio 600 57.94 66.09 33.01 2.60 650 67.88 73.2526.75 2.45 700 73.47 80.9 19.1 2.12 750 86.83 86.63 13.37 2.04 800 93.4193.89 6.11 2.00 900 94.83 96.23 3.77 1.99 Reaction conditions: P: 100kPa (1 bar), GHSV: 18,600 h⁻¹. Pure oxygen was used as the oxidant.

EXAMPLE 4

1.0 g of α-Al₂O₃ support (particle size>250 μm) was impregnated with 1.0ml of 0.12 M Pr(NO₃)₃ solution for 10 h while stirring. It was thencalcined at 650° C. for 2 h. The resulting Pr₂O₃ modified support(Al₂O₃—Pr₂O₃) (1.05 g) was impregnated with 1 ml of 1.0 M Co(NO₃)₂solution for 5 hours. The solid was calcined to 700° C. and held for 2h, then cooled to room temperature. The resulting oxide precursor wasthen treated with 30 ml/min of CH₄ at 700° C. for 5 h and then cooled toroom temperature. The activated catalyst was treated with 1.0% O₂/N₂ for10 hours. The ready-for-use catalyst (0.1 g) was loaded in a quartztube, heated to 860° C. in N₂, and then a mixture of CH₄ and air (CH₄/O₂ratio, 2.01) was introduced into the reactor at several different flowrates and at 100 kPa (1 bar). The reaction conditions and productdistribution are listed in Table 4.

TABLE 4 Effect of space velocity on CH₄ conversion and productdistribution from POM over 5.6 wt % Co/Al₂O₃—Pr₂O₃ catalysts activatedwith pure CH₄ to 700° C. for 1 h CH₄ CO CO₂ GHSV conversion selectivityselectivity H₂/CO (h⁻¹) (%) (%) (%) ratio 6,000 95.43 96.57 3.43 1.9912,000 95.21 95.98 4.02 2.00 25,000 94.62 96.02 3.98 2.01 40,000 90.8992.53 7.47 1.98 60,000 92.5 92.9 7.1 1.99 Reaction conditions: P: 100kPa (1 bar), reaction temperature: 860° C., air was used as the oxidant.

EXAMPLE 5

1.0 g of the BaO modified support (Al₂O₃—BaO) was impregnated with 1 mlof 0.75 M Co(NO₃)₂ solution for 5 hours. The solid was calcined to 750°C. and then cooled to room temperature. It was then treated with 14ml/min of C₂H₆ at 600° C., and then cooled to room temperature. Theactivated catalyst was treated with 1.0 O₂/N₂ for 3 h. The ready-for-usecatalyst (0.1 g) was placed in a quartz tube, and heated to the selectedreaction temperatures in N₂. A mixture of C₂H₆ and air (C/O ratio, 1.0)was passed into the reactor at 100 kPa (1 bar). The product distributionis shown in Table 5.

TABLE 5 C₂H₆ conversion and product distribution from POM over 4.0 wt %Co/Al₂O₃—BaO catalysts activated with pure ethane to 600° C. for 2 hReaction temperature C_(C2H6) S_(CH4) S_(CO) S_(CO2) H₂/CO (° C.) (%)(%) (%) (%) ratio 750 80.49 0.8 90.36 8.84 1.96 800 93.40 1.1 96.75 2.152.02 900 95.82 1.2 97.61 3.19 1.99 Reaction conditions: P: 100 kPa (1bar), GHSV: 25,000 h⁻¹, air was used as the oxidant.

EXAMPLE 6

1.0 g of the BaO modified support (Al₂O₃—BaO) was impregnated with 1 mlof 1.0 M CoC₂O₄ solution for 4 hours. The solid was dried at 100° C. for3 h, calcined to 700° C. and held for 2 h, then cooled to roomtemperature. The resulting oxide precursor was treated with 30 ml/min ofa mixture of 20% C₂H₆/H₂ to 750° C. and held for 2 h. It was then cooledto room temperature and treated with 1.0% O₂/N₂ for 2 h. Theready-for-use catalyst (0.1 g) was loaded in a quartz tube, heated tothe selected reaction temperatures in static 20% C₂H₆/H₂ and held for0.5 hours. A mixture of CH₄ and air (containing steam) (C/O ratio 1.0;H₂O/CH₄ ratio 1.0) was introduced into the reactor at 100 kPa (1 bar).The reaction conditions and product distribution are listed in Table 6.

TABLE 6 CH₄ conversion and product distribution from oxy-steamcombination reforming of methane over 5.6 wt % Co/Al₂O₃—BaO catalystsactivated with mixture of ethane and hydrogen to 750° C. for 2 hReaction CH₄ CO CO₂ temperature conversion selectivity selectivity H₂/CO(° C.) (%) (%) (%) ratio 800 81.68 92.56 7.44 1.99 830 85.95 94.58 5.422.02 900 91.46 96.47 3.53 2.09 Reaction condition: P: 100 kPa (6 bar),GHSV: 25,000 h⁻¹, air was used as the oxidant.

EXAMPLE 7

1.0 g of the BaO modified support (Al₂O₃—BaO) was impregnated with 1 mlof 1.0 M Co(NO₃)₂ solution for 5 hours. The solid mixture was dried at100° C. for 3 h, and calcined at 650° C. for 2 h. The resulting oxideprecursor of the catalyst (0.1 g) was placed in a quartz tube andtreated with 20 ml/min of a mixture of 10% CH₄/H₂ or H₂ to 800° C. for 2hours. The reactant gas was then switched to a mixture of CH₄ and air(C/O ratio 1.0), and the temperature was increased to 850° C. The carbondeposition was measured after 200 h run, and the reaction was continueduntil the CH₄ conversion decreased to less than 90%. The reactionconditions and results are listed in Table 7.

TABLE 7 Carbon deposition amount* and lifetime of 5.6 wt % Co/Al₂O₃—BaOcatalysts activated with CH₄/H₂ and pure H₂ to 800° C. for 2 h CatalystAmount of carbon Life-time activated with deposition (%) (h)** CH₄/H₂0.9 >1000 H₂ 6.6 260 Reaction conditions: P: 10 kPa (1 bar),Temperature: 850° C., GHSV: 25,000 h⁻¹, air was used as the oxidant.*The amount of carbon was measured after 200 hour time-on-stream.**Life-time is when the catalyst activity is reduced to less than 90%.

EXAMPLE 8

0.2g of SiO₂ (>250μm, dried at 200° C. for 4 h) was impregnated with 0.4ml of water solution (containing 2.5M Co(NO₃)₂ and 0.2M ZrO(NO₃)₂) atroom temperature, for 10 hours. The system was calcined at 450° C. for 4h in air, cooled to room temperature, and then activated with 10% CH₄/H₂at a temperature gradient of 2K/min to 500° C. and held for 1 h. Then itwas cooled to 230° C., and the gas was changed to a mixture of 9 ml/minsyngas (2H₂+CO) and 1 ml/min N₂, with the pressure being increased to600 kPa (6 bar). The mass balance and product distribution are shown inTable 8.

TABLE 8 Mass balance for F-T synthesis after 48 hour time-on-streamReaction conditions: 230° C., 600 kPa (6 bar), 0.2 g CoZr/SiO₂ catalystactivated with 10% CH₄/H₂ Gas Supplied Carbon Hydrogen Oxygen Nitrogenml/min mg/min mg/min mg/min mg/min mg/min Hydrogen 5.73 0.51 0.51 N₂0.70 0.87 0.87 CO 2.87 3.59 1.54 2.05 Total 9.30 4.97 1.54 0.51 2.050.87 Calculated from GC analyses Conversion Selectivity vol % ml/minmg/min mg/min mg/min mg/min (%) (%) Hydrogen 40.65 1.62 0.144 0.00 0.140.00 71.8 Nitrogen 17.61 0.70 0.874 0.00 0.00 0.00 Methane 6.80 0.270.193 0.14 0.05 0.00 14.18 CO 24.26 0.96 1.205 0.52 0.00 0.69 66.4 CO₂1.21 0.05 0.095 0.03 0.00 0.07 2.53 C₂ 0.76 0.03 0.040 0.03 0.01 0.003.17 C₃ 2.02 0.08 0.154 0.13 0.01 0.00 12.62 C₄ 2.47 0.10 0.249 0.210.04 0.00 20.57 C₅ 2.38 0.09 0.300 0.25 0.05 0.00 24.81 C₆ 1.45 0.060.218 0.18 0.03 0.00 18.10 C₇ 0.40 0.02 0.071 0.06 0.01 0.00 5.84 Total100.00 3.97 3.543 1.56 0.35 0.76 H₂O O₂ Balanced 1.79 1.435 0.14 1.29liquid H₂ Balanced 0.116 0.10 0.017 9.72 product Carbon Balance GCanalysis All products Misc. Nitrogen 100.0 100.0 GHSV (/hour) 1860Oxygen 37.0 100.0 Gas Velocity (mm/s) 1.98 Hydrogen 68.5 100.0 Carbon101.2 107.7

EXAMPLE 9

1.0 g of γ-alumina (dried at 120° C. for 4 hours) was impregnated with0.8 ml of 0.5 La(NO₃)₃ solution at room temperature for 2 hours whilestirring. The mixture was left to stand in air for 20 hours, afterwardscalcined at 600° C. for 4 hours, and then cooled to room temperature.The La modified alumina was then impregnated with 1 ml of 0.8 MCo(NO₃)₃.6H₂O solution, the mixing stirred at room temperature for 4hours, and left to stand in air for 6 hours. It was then calcined at600° C. for 4 hours to provide a Co₃O₄/Al₂O₃—La catalyst precursor formethane partial oxidation to synthesis gas.

0.01 g of the above catalyst precursor was loaded in a 6 mm (o.d) silicatube lined stainless steel reactor and treated with 4 ml/min of pure CH₄to 900° C., and held at 900° C. for 30 minutes. Then a mixture stream of(6.1 ml/min CH₄+2.5 ml/min O₂ (pure)) was passed to the catalyst bed andthe pressure increased to 800 kPa (8 bar). The catalyst performance isshown in Table 9.

TABLE 9 Selectivity H₂/CO Tested time X_(CH4) to CO ratio (Hours)Catalyst 80.5% 98.7% 1.99 800 performance

Reaction temperature: 950° C.; pressure 800 kPa (8 bar) Feedstockcomposition: 2.5 CH₄/O₂, pure O₂ was used as the oxidant; excess methanewas fed to eliminate the thermodynamic effect and increase yield andselectivity to CO₂ and H₂.CH₄ conversion and CO₂ selectivity were betterin using air as the oxidant.

GHSV: 516,000 h⁻¹.

This makes it possible to configure a direct Fisher-Tropsch synthesis.

1. An activated catalyst comprising 0.02% to 10 wt % carbon which isobtainable by a process comprising activating a catalyst precursorcomprising a cobalt compound and a support with a gas comprising atleast 5 mol % of at least one hydrocarbon selected from the groupconsisting of methane, ethane, acetylene, propane, propene and butane,at a temperature of at least 300° C., wherein the catalyst precursor isa POM, Fisher-Tropsch, hydroisomerisation or hydrogenation catalystprecursor that comprises 0.05 to 30 wt % cobalt.
 2. A catalyst accordingto claim 1 wherein the support is alumina, modified alumina, silica,modified silica, B-aluminate, magnesia, titania, a spinel oxide,zirconia, a zeolite or carbon.
 3. A catalyst according to claim 1wherein the hydrocarbon is methane or ethane.
 4. A catalyst according toclaim 1 wherein the catalyst precursor is activated at a temperature offrom 300° C. to 1000° C.
 5. A catalyst according to claim 1 wherein thegas comprises at least 10 mol % of the hydrocarbon.
 6. A catalystaccording to claim 5 wherein the gas comprises at least 20 mol % of thehydrocarbon.
 7. A catalyst according to claim 1 wherein the gas alsocomprises H₂, N₂, argon, helium or a mixture thereof.
 8. A catalystaccording to claim 7 wherein the gas comprises H₂ and the ratio ofhydrocarbon to hydrogen is from 0.04 to 10:1 on a molar basis.
 9. Acatalyst according to claim 1 wherein the gas consists only of thehydrocarbon.
 10. A catalyst according to claim 1 wherein the catalystprecursor is prepared by impregnating the support with a solution of acobalt salt.
 11. A catalyst according to claim 10 wherein the cobaltsalt is cobalt nitrate, acetate or oxalate.
 12. A catalyst according toclaim 1 wherein the catalyst precursor has been prepared by a sol gelmethod.
 13. A catalyst according to claim 1 wherein the catalystprecursor is calcined before activation.
 14. A catalyst according toclaim 13 wherein the catalyst precursor is calcined at a temperature offrom 300 to 1000° C.
 15. A catalyst according to claim 1 wherein theactivated catalyst is pacified by treatment in a reduced oxygenatmosphere for at least 30 minutes.
 16. A catalyst according to claim 1wherein the gas consists essentially of said hydrocarbon and optionallyan inert gas and/or hydrocarbon.
 17. A process for the partial oxidationof a hydrocarbon which comprises passing the hydrocarbon and oxygen overa catalyst according to claim
 1. 18. A process according to claim 17wherein the hydrocarbon is methane and the partial oxidation producessyngas.
 19. A process according to claim 17 wherein the atomic ratio ofcarbon to oxygen in the feedstock is 0.9 to 5:1.
 20. A process accordingto claim 17 wherein the oxygen is present in the form of a mixture of O₂and H₂O; O₂ and CO₂; or O₂, H₂O and CO₂.
 21. A process according toclaim 17 wherein the oxygen is diluted with N₂, Ar, or He.
 22. A processfor the preparation of a mixture of hydrocarbons by Fischer-Tropschreaction, which comprises passing a mixture of carbon monoxide and H₂over a catalyst according to claim 1.